Writing on his Facebook page, Brigadier-General (NS) Tan said he received information of this agency through someone who wrote to him.
BG Tan said: "We have had a 'chat' with the recruitment agency and they have immediately remedied the discriminatory practice."
He added the incident reiterates the need for fair play when it comes to hiring, and the need to hire on merit.
He said employers and recruiters must not lose sight of this.
BG Tan also spoke of some key issues which have been occupying him and the team in the Manpower Ministry over the past few weeks.
One key issue, he said, was to keep the country growing to provide good jobs for young Singaporeans coming of age every year.
Another was keeping Singapore ahead of global competition while sensibly managing the size of the foreign labour force.
He said tightening the foreign labour market is do-able, but there can be important implications if it is over done or tweaked in the wrong sectors.
BG Tan said most Singaporeans recognise that the country will continue to need foreign workers and foreign talents.
"We know that we need to tighten foreign workforce inflow and we have done so," BG Tan said.
"Foreign worker levies are being progressively increased over the next two years. We will also raise salary thresholds for semi-skilled (S Pass) and professionals in Singapore at the same time."
The S Pass would be raised from S$1,800 to S$2,000 per month, while the Employment Pass (EP) would be raised from S$2,500 to S$2,800.
BG Tan added: "We will also aim to keep overall numbers down at one-third of overall work force".
He said the ministry will keep a close watch on how these measures work from July.
